This invention pertains to the arts of high speed data and digital telephony interconnect, wiring, termination, and routing technologies, especially those technologies related to provision of redundant, switch-over, back-up or protection of critical interconnects.
This invention was not developed in conjunction with any Federally-sponsored contract.
The related application, docket number, filed on May 3, 2000, by Steven Dale Sensel, et al, is incorporated herein by reference in its entirety, including drawings, and is hereby made a part of this application.
High speed data and digital telelphony interconnection schemes are well-known within the art of data and telecommunications, including multi-megabit to gigabit-per-second data rates such as North American transmission standards including STS-1 electrical, STS-3 electrical, VT1.5 electrical, DS-1/T1, DS-3/T3, 25M asynchronous transfer mode (xe2x80x9cATMxe2x80x9d), asynchronous digital subscriber line (xe2x80x9cADSLxe2x80x9d), high-speed digital subscriber line (xe2x80x9cHDSLxe2x80x9d), and optical media such as OC-1, OC-3, OC-12, OC-48, OC-192, OC-768; international optical standard media such as synchronous digital hierarchy (xe2x80x9cSDHxe2x80x9d) STM-1, STM-4, STM-16, and STM-64; various standards from the European Telecommunications Standards Institute (xe2x80x9cETSIxe2x80x9d) and the International Telecommunications Union (xe2x80x9cITUxe2x80x9d) E1 and E3; Japanese standards including J1 and J2; and local area network (xe2x80x9cLANxe2x80x9d) interfaces and transmission protocols such as EtherNet, Fast EtherNet, Giga-bit EtherNet, and Token Ring.
Because of the transmission line characteristic and signal integrity considerations necessary to successfully route and interconnect signals of these frequencies, great care must be taken to avoid termination impedance mismatches, unnecessary stubs, and cross talk. Most cabling and connectors used in these installations are either twisted-pair and/or shielded designs.
Most telecommunications switching and data routing systems (10) are organized into xe2x80x9cshelvesxe2x80x9d (11) of cards (12), each card having a particular function in the overall system, as shown in FIG. 1. For example, it is common to have line interface cards which interface to a particular type of media, such as STS-1 or DS3, and to have a shelf processor card which controls and coordinates the functions of the line interface cards. The cards typically install from the xe2x80x9cfront panelxe2x80x9d of the rack in which the shelves are installed, and mate to a backplane towards the rear of the shelf. The backplane provides power distribution as well as functional interconnects such as switching busses, data and address busses, and specialized control and status signals. System architectures such as this are well-known within the art.
In order to provide for greater reliability of a shelf or system, many systems include backup or xe2x80x9cprotectionxe2x80x9d cards or card slots. These cards are typically idle and kept on-line as spare cards for use in the event a primary card fails. In a one-for-one protection scheme (xe2x80x9c1:1xe2x80x9d), each functional card has a paired protection card. So, if a shelf contains 4 DS-3 interface cards, there would be 4 protection DS-3 cards. In a one-for-xe2x80x9cNxe2x80x9d (xe2x80x9c1:Nxe2x80x9d) protection scheme, there are more active or primary cards than protection cards. For example, if there are 4 active DS-3 interface cards and a single protection DS-3 card in a shelf, it is called a 1:4 protection scheme.
Routing of the signal to the protection card or cards is also provided in several convention ways. In many systems, the signal cables, such as DS-3 coax cables or twisted pair cables, connect to the system on the back side of the backplane or to small cards installed from the back panel. This is called xe2x80x9cback panelxe2x80x9d access. In such a case, the signals are usually routed to the protection card or cards and the primary card slots on the backplane itself, providing a 2-for-1 split for 1:1 protection schemes, or a many-for-1 bussing arrangement for a 1:N protection scheme.
In other systems, front panel access is required, such that signal cables (13) are connected to the front edge of the line interface cards, as shown in FIG. 1. While this access arrangement is preferred by many telephone operating companies, it is actually required under certain national and regional telecommunications norms such as those promulgated by the European Telecommunications Standards Institute (xe2x80x9cETSIxe2x80x9d). Re-routing of the signal from the front panel connection to a failed or out-of-service card to a protection card presents particular obstacles in this case. Some systems have simply make connection to the backplane through a passive extender card, but this is not an optimal solution as one card slot is dedicated to this interconnect card and functionality for that slot is lost.
Additionally, systems are typically designed for a certain protection scheme, such as 1:1 or 1:4, etc., and the slots in the shelf are specialized to house primary cards and protection cards because the backplane may be xe2x80x9chardwiredxe2x80x9d to create a given shelf topology. This restricts the use of the shelf for alternate applications, and thus reduces the number of installations in which a particular shelf design may be deployed. This drives a need for a variety of shelf topologies, which increases production and maintenance costs. For example, a shelf that provides DS-3 switching may have one version which supports 1:1 protection such that half of the cards in the shelf are primary cards and half of the cards are protection cards. This particular shelf would be useful for installations in environments where the traffic carried on the DS-3 links is very critical, such as switch rooms for emergency services. However, for installations into switch rooms for low-cost long distance service providers, the 50% unused functionality may be unacceptable. These low-cost long distance service providers may prefer a 1:8 protection scheme in their shelves, allowing for 8 primary DS-3 interface cards carrying active traffic, with 1 protection card on standby. But, the shelf which provides 1:1 protection cannot be deployed for the 1:8 use, and vice versa.
Therefor, there is a need in the art for a telecommunications interconnect method and system which allows for configuration and re-configuration of the protection scheme. This system must allow the protection scheme to be useful for high-speed as well as low speed data applications to meet the demands of the wide array of telecommunications xe2x80x9cphysical layersxe2x80x9d (e.g. DS-1, E1, DS-3, STS-1, OC-1, etc.). Further, it is preferable that this system and method provide front panel connectivity without dedication of card slots for interconnect of signals to the backplane. Additionally, it is preferable that the protection scheme be compatible with the cabling scheme of the related application, but not be dependent upon this cabling scheme for realization of the invention.
The present invention is useful for data and telecommunications signals at all speeds and frequencies in the electrical domain, and also for signals in the optical domain, including including multi-megabit to gigabit-per-second data rates such as North American transmission standards including STS-1 electrical, STS-3 electrical, VT1.5 electrical, DS-1/T1, DS-3/T3, 25M asynchronous transfer mode (xe2x80x9cATMxe2x80x9d), asynchronous digital subscriber line (xe2x80x9cADSLxe2x80x9d), high-speed digital subscriber line (xe2x80x9cHDSLxe2x80x9d), and optical media such as OC-1, OC-3, OC-12, OC-48, OC-192, OC-768; international optical standard media such as synchronous digital hierarchy (xe2x80x9cSDHxe2x80x9d) STM-1, STM-4, STM-16, and STM-64; various standards from the European Telecommunications Standards Institute (xe2x80x9cETSIxe2x80x9d) and the International Telecommunications Union (xe2x80x9cITUxe2x80x9d) E1 and E3; Japanese standards including J1 and J2; and local area network (xe2x80x9cLANxe2x80x9d) interfaces and transmission protocols such as EtherNet, Fast EtherNet, Giga-bit EtherNet, and Token Ring. A daisy-chain alternate signal path, signal selectors, and alternate front panel entry points are provided to a front-access telecommunications shelf system. Cards can be designated as primary cards to handle traffic under normal conditions, or as protection cards, without hardware constrained or slot-specific card requirements. Variations of 1:N protection, and multiple groups of 1:N configurations and partitions can be defined without changes to cabling or backplane design variations through setting of relays and signal selectors on each card. As such, any signal present on a cable connected to a primary card may be re-routed to any card designated as a protection card, by first routing the signal through a protection relay on the failed card to a cable to a neighboring card, through a data selector on the neighboring card onto the backplane, and to a selected protection card.